The present invention relates to a current breaker circuit for cutting off a plurality of storage devices connected in series, and load circuits (voltage detection circuit) for the respective storage devices in accordance with a single external signal so that a leakage current can be prevented; to a voltage detection circuit for such storage devices; and an abnormality detection circuit.
In a circuit in which a plurality of storage devices are connected in series and loads are connected to the storage devices respectively, it has been heretofore necessary to prevent consumption of energy accumulated in the storage devices.
To this end, there have been related-art current breaker circuits as shown in FIGS. 6 and 7. Such current breaker circuits can disconnect all the loads in accordance with a single control signal when the storage devices and the loads are disconnected respectively.
The configurations and operations of the related-art circuits will be described below with reference to FIGS. 6 and 7.
FIG. 6 shows an example of a related-art current breaker circuit.
In FIG. 6, storage devices B1 to B4 are connected in series. In addition, loads R1 to R4 are connected to the storage devices B1 to B4 respectively.
In addition, semiconductor switching devices Q1 to Q4 are connected between the storage devices B1 to B4 and the loads R1 to R4 respectively.
The bases of the semiconductor switching devices Q1 to Q4 which are control terminals are connected in common through diodes d1 to d4 and resistors r1 to r4 so that an external signal switch S provided between the common connection terminal and the negative terminal of the storage device B1 can be turned ON or OFF in accordance with an ON/OFF signal.
As for the operation of this current breaker circuit, when the external signal switch S provided between the common connection terminal of the resistors r1 to r4 and the negative terminal of the storage device B1 is turned ON in accordance with the ON/OFF signal supplied to the switch S, all the semiconductor switching devices Q1 to Q4 are turned ON. Thus, currents are supplied from the storage devices B1 to B4 to the loads R1 to R4 corresponding and respectively.
On the contrary, when the external signal switch S is turned OFF, the semiconductor switching devices Q1 to Q4 are turned OFF so that no current is supplied to the loads R1 to R4.
In this current breaker circuit, all the semiconductor switching devices Q1 to Q4 can be turned ON/OFF in accordance with a single ON/OFF signal. However, on the higher potential side (the storage device B4 side in FIG. 6) of the storage devices connected in series, the voltage between the emitter of the semiconductor switching device and the negative terminal of the storage device B1 increases. Thus, there is a problem that the power loss of the resistor increases and a high voltage switch has to be used as the external signal switch S.
FIG. 7 shows another example of a related-art current breaker circuit.
In FIG. 7, storage devices B1 to B4 are connected in series in the same manner as those in FIG. 6.
In addition, loads R1 to R4 are connected to the storage devices B1 to B4 respectively.
In addition, photo-couplers (photo-relays) PH1 to PH4 are connected between the storage devices B1 to B4 and the loads R1 to R4 respectively.
All of light-emitting diodes of the photo-couplers PH1 to PH4 are connected in series, and designed so that a current is supplied between opposite terminals of each light-emitting diode in accordance with an ON/OFF signal given to the switch S.
As for the operation of this current breaker circuit, all the photo-couplers PH1 to PH4 are turned ON when a current is supplied to the light-emitting diodes connected in series. Thus, currents are supplied from the storage devices B1 to B4 to the loads R1 to R4 respectively.
On the contrary, when no current is supplied to the light-emitting diodes connected in series, all the photo-couplers PH1 to PH4 are turned OFF. Thus, no current is supplied to the loads R1 to R4.
In this current breaker circuit, all the semiconductor switching devices Q1 to Q4 can be turned ON/OFF in accordance with a single ON/OFF signal. Accordingly, the problem of withstanding voltage as in the circuit of FIG. 6 is solved. On the other hand, there is however a problem that a large number of expensive photo-couplers or the like have to be used.
In order to solve the defects in the related-art current breaker circuits, an object of the invention is to provide a current breaker circuit which can surely break currents supplied to a plurality of loads from a plurality of storage devices connected in series, in accordance with a single external control signal without using any high-voltage withstanding switch or any expensive photo-coupler; and to provide a voltage detection circuit for such storage devices.
In addition, another object of the invention is to provide an abnormality detection circuit for such a current breaker circuit.
To solve the foregoing problems, according to the invention, there is provided a current breaker circuit for turning off currents flowing in loads in accordance with a single external control signal, while the loads are connected between terminals of a plurality of storage devices connected in series respectively. The current breaker circuit includes semiconductor switching devices inserted between the storage devices and the loads respectively, a unit for supplying the external control signal to at least one of the semiconductor switching devices, and a control signal generating unit for generating an ON/OFF signal in response to an electric change based on turning ON/OFF of the semiconductor switching device supplied with the external control signal, the ON/OFF signal being supplied to other semiconductor switching devices.
Accordingly, currents supplied from the plurality of storage devices connected in series to the plurality of loads can be surely broken in accordance with a single external control signal without using any high-voltage withstanding switch or any expensive photo-coupler.
The loads in this configuration may be formed as pieces of a voltage detection circuit for storage devices. In this case, the current breaker circuit for storage devices has features in that:
(1) a plurality of storage devices are connected in series;
(2) a piece of the voltage detection circuit is connected for every unit cell of the plurality of storage devices;
(3) each piece of the voltage detection circuit is connected between a positive terminal and a negative terminal of a corresponding unit cell of the plurality of storage devices;
(4) a semiconductor switching device is inserted between the storage device and the voltage detection circuit;
(5) a control signal generator circuit for supplying a control signal to a control electrode of the semiconductor switching device inserted in series is connected to the control electrode of the semiconductor switching device; and
(6) the control signal generator circuit detects a voltage change on the voltage detection circuit side of the semiconductor switching devices connected to the storage devices other than the storage device to which the semiconductor switching device for supplying the control signal is connected, and the control signal generator circuit generates the control signal in accordance with the detection of the voltage change.
In addition, when the external control signal is supplied to at least two adjacent ones of the semiconductor switching devices simultaneously, the current breaker circuit for storage devices can be formed out of a smaller number of constituent members.
In addition, when the control signal generating unit supplies the ON/OFF signal to at least two adjacent ones of the semiconductor switching devices simultaneously, the number of the control signal generator circuits can be reduced.
In addition, when the semiconductor switching device supplied with the external control signal is formed as a semiconductor switching device connected to a lower voltage side among the storage devices connected in series, the potential of the switch can be made lower.
In addition, when the ON/OFF signal is supplied to the semiconductor switching devices through diodes respectively, high voltage can be prevented from being applied to the control terminals of the semiconductor switching devices.
In addition, when the loads are formed as a voltage detection circuit for detecting terminal-to-terminal voltages of the plurality of storage devices connected in series, even a very small current flowing in the voltage detection circuit can be broken surely.
Further, a voltage detection circuit for storage devices according to the invention has features in that:
a plurality of terminal-to-terminal voltage generator circuits are provided;
each of the terminal-to-terminal voltage generator circuits is constituted by a storage device, a subtractor circuit and an A/D converter circuit, the subtractor circuit being supplied with a positive terminal voltage (Vn+1) and a negative terminal voltage (Vn) of the storage device and outputting a terminal-to-terminal voltage (Vno) of the storage device, the A/D converter circuit being supplied with the output of the subtractor circuit and outputting digital data;
the storage devices provided in the plurality of terminal-to-terminal voltage generator circuits are connected in series;
outputs of the A/D converter circuits provided in the plurality of terminal-to-terminal voltage generator circuits are supplied to a selector circuit, which selects one piece of output data from the parallel output data supplied from the plurality of A/D converter circuits; and
the selected piece of output data is supplied to a parallel-to-serial converter circuit, which converts the piece of output data into serial data, and outputs the converted serial data, so that a terminal-to-terminal voltage of any desired one of the plurality of storage devices connected in series is obtained as the serial data.
In the voltage detection circuit for storage devices configured thus, the terminal-to-terminal voltages of the plurality of storage devices connected in series can be detected accurately and selectively respectively to be outputted.
In addition, an external select control signal may be supplied to the selector circuit.
In addition, a plurality of parallel-to-serial converter circuits may be provided at a pre-stage of the selector circuit so that the selector circuit can select one from the outputs converted into serial data by the parallel-to-serial converter circuits.
In addition, when the serial data and/or the select control signal are supplied through an isolator, the serial data and/or the select control signal can be electrically isolated from external circuits.
Further, a voltage detection circuit for storage devices according to the invention has features in that:
at least a plurality of terminal-to-terminal voltage generator circuits are provided;
each of the terminal-to-terminal voltage generator circuits is constituted by a storage device, a subtractor circuit and an A/D converter circuit, the subtractor circuit being supplied with a positive terminal voltage (Vn+1) and a negative terminal voltage (Vn) of the storage device and outputting a terminal-to-terminal voltage (Vno) of the storage device, the A/D converter circuit being supplied with the output of the subtractor circuit and outputting digital data;
the storage devices provided in the plurality of terminal-to-terminal voltage generator circuits are connected in series;
a selector circuit selects one piece of output data from output data of the A/D converter circuits respectively provided in the plurality of terminal-to-terminal voltage generator circuits; and
the selected piece of output data is supplied to a parallel-to-serial converter circuit, which converts the supplied piece of output data into serial data;
the terminal-to-terminal voltage generator circuits, the selector circuit and the parallel-to-serial converter circuit are included in a single module; and
a pair of opposite terminals of the plurality of storage devices connected in series, and an output terminal of the serial data are led out as external terminals of the module.
When the single module is configured thus, a desired system can be constructed easily by use of a plurality of such modules.
In addition, when a select control signal from the outside of the module is supplied as a serial signal to the selector circuit, signals can be transmitted/received between the module and the outside through a small number of signal lines.
In addition, a plurality of parallel-to-serial converter circuits may be provided at a pre-stage of the selector circuit so that the selector circuit can select one from the outputs converted into serial data by the parallel-to-serial converter circuits.
In addition, an isolator for electrically isolating the serial data and/or the select control signal may be provided in the module.
Further, according to the invention, an abnormality detection circuit for detecting abnormality of a current breaker circuit breaking currents in accordance with a single external control signal is provided. The currents flow into a plurality of loads which are respectively connected between terminals of a plurality of storage devices connected in series. When operation abnormality of the current breaker circuit is detected on the basis of the single external control signal and a terminal-to-terminal voltage of a final-stage one of the loads in the abnormality detection circuit, abnormality of the operation of the current breaker circuit as a whole can be detected easily.
In addition, a first photo-coupler and a second photo-coupler may be provided and connected in series to opposite terminals of the final-stage load respectively. In this case, the external control signal is supplied to the second photo-coupler only for an abnormality detection period so as to turn on the abnormality detection circuit and thereby obtain a detection result through the first photo-coupler. Thus, a current is allowed to flow into a light emitting device of the first photo-coupler and a light receiving device of the second photo-coupler only for the detection period. Accordingly, it is not necessary to make a constant conduction. It is therefore possible to prevent useless consumption of electric power.